The present invention relates to labels, especially to labels that are particularly adapted for use in in-mold labeling of blow-mold polyethylene containers. More particularly, the present invention relates to a coextruded plastic film label for use in such in-mold labeling applications.
The in-mold labeling of blow-mold polyethylene containers, particularly blow molded high density polyethylene containers allows the manufacturer to readily and inexpensively produce labeled containers directly from the molding operation without the need to apply adhesively backed labels in a subsequent step. By eliminating subsequent handling and adhesive applying operations capital investment and handling costs are substantially reduced. However, in-mold labeling equipment requires the cooperation of various mechanical devices which operate at relatively high speeds. Labels are supplied from a magazine and individually positioned by a mechanical or vacuum operated device inside of a mold which is thereafter closed and the molded thermoplastic object prepared. Blow molding is a suitable molding process wherein a parison of heat plastified thermoplastic resin, most generally high density polyethylene, is extruded and then expanded to conform to the inner surface of a mold. The label, which also must conform to the inner surface of the mold, must be held in place until contacted with the heat plastified thermoplastic resin and thereafter must become attached to the resulting object by means of a heat activated adhesive contained on the surface of the label.
The entire procedure must be carried out in a continuous and rapid manner. The supply of labels from a suitable magazine, the positioning of the label within the mold, and the blow molding procedure must proceed in an uninterrupted manner in order to attain desired economical level of operation. Accordingly, labels for use in in-mold labeling processes are required to meet demanding performance requirements. Suitably, the labels must be sufficiently stiff that wrinkling or folding does not occur during handling by the automated equipment. Contrarywise, the labels are required to be sufficiently elastic or flexible that upon attachment to the desired blow molded object they will remain adhered thereto without splitting or separating despite bending, flexing, or squeezing of the finished container.
For certain applications the container, especially shampoos containers, laundry detergent containers, etc. may be exposed to high humidity or water. The adhesive used to adhere the label to such a container should desirably resist the effects of moisture which may lead to delamination or wrinkling of the label.
A further requirement of in-mold labels is the presence of a suitable surface appearance. It is highly desirable from an esthetical and consumer acceptance point of view that the label not affect graphics or printing appearing on the surface thereof. Because thermoplastic scrap generated in the manufacture of coextruded films is desirably reused by recycling, i.e., regrinding and remelting, and incorporating the same into a separate inner layer of the film, it is highly desirable in the preparation of such labels that such scrap containing layer within the label not affect surface qualities of the label itself.
Finally, previously known in-mold labels prepared from cellulosic base stocks, such as paper, have proven undesirable in operation because the recycle of scrap blow-molded objects having such labels affixed thereto requires tedius mechanical means or solvents to first remove the labels. In order to reclaim or recycle such bottles, particularly defective bottles prepared during the blow-molding process, it is first necessary to remove the paper labels. Contamination by residual adhesive and small portions of unremoved paper may make it practically impossible to reclaim defective blow-molded containers bearing such labels. As an alternate means of disposal, defective containers must be burned or buried in landfills both of which practices are wasteful and undesirable.
It would be desirable to provide a polymeric label particularly adapted for use in in-mold labeling of blow-molded polyethylene containers.
In addition, it would be desirable to provide such a label for use in in-mold labeling which combines suitable properties of modulus of elasticity and flexibility, and at the same is adaptable to in-mold processing conditions and not degraded by flexing and handling of the subsequent container.
It would further be desirable to provide a label for use in in-mold labeling applications which is unaffected by moisture or high humidity environments.
Finally, it would be desirable to provide a label for in-mold labeling operations which does not have to be removed from such containers in order to recycle or regrind defective thermoplastic containers for subsequent incorporation into the thermoplastic.